A wind turbine blade usually comprises a composite laminate structure. The composite laminate structure is typically manufactured using fibre reinforcing material embedded in a polymer matrix. The laminate structure is typically formed by a plurality of stacked fibre layers. Today, the fibre layers are mostly selected from glass fibres or carbon fibres or a hybrid material comprising both glass fibres and carbon fibres.
To protect wind turbine blades from lightning damages, wind turbine blades are equipped with a lightning protection system. For wind turbine blades being reinforced with electrically conductive fibres, such as carbon fibres, the efficiency of the lightning protection system depends on having a conductivity property through the thickness of the composite laminate structures. The electrically conductive fibres are typically potentially equalised to the lightning protection system, advantageously to a down-conductor of the lightning protection system, at different positions or areas along the span of the blade.
The load carrying structure is typically manufactured by infusing stacked fibre layers with resin. To aid the resin flow during infusion, a flow media may be needed. This is particularly the case for carbon fibres due to the small size of the fibres and hence the size of spacings or voids between the fibres. However, placing a conventional flow media isolates or separates each fibre layers from one another. This results in significantly reducing the conductivity in between each carbon fibre layers.
There is thus a need for a solution that provides both flow for the resin to be infused and conductivity through stacked fibre layers.